Development, Application, and Validation of the Urban Flood Susceptibility Index

Modifications to the landscape for urban expansion directly impact the natural hydrological dynamics in Urban Hydrographic Micro-basins (UHMs). This study aims to develop the Urban Flood Susceptibility Index (UFSI) from indicators pertinent to different spheres, considering both infiltration and surface runoff of rainwater, and apply it in UHMs of a municipality in the Midwest Region of Brazil. Historical records of urban floods available in information media are used to validate the UFSI. The methodology adopted involves the Analytical Hierarchical Process linked to the Geographic Information System. UFSI is composed of the following indicators: average slope (Sa), coefficient of compactness (Kc), drainage density (Dd), demographic density (Ddem), degree of surface permeability (DSP), susceptibility to production of sediment (SPS), daily precipitation (Pd), degree of canalization of watercourses (DCW), condition of storm drains (CSD), and rainwater retention devices (RRD). Therefore, USFI simultaneously includes morphometric, environmental, land use and occupation, and urban infrastructure indicators. Pd (0.16 for both dimensions) and DSP (0.15 for surface runoff and 0.26 for infiltration) indicators are the most significant for urban flood susceptibility in both analysed dimensions. Sa (0.15) and DCW (0.14) are relevant in relation to surface runoff, while RRD (0.13) and SPS (0.09) regarding to infiltration. UFSI and historical records of each UHM obtained strong correlation (r > 0.80), evidencing reliability and validation of the index. The UFSI can assist in the formulation of guidelines for land use and occupation and to indicate UHMs that require attention from the public authority for sustainable socioeconomic development.